Getting the Best Possible Sound from a Piezo Electric Pickup
Most acoustic guitars that come with built in pickups, use piezo-electric technology for the pickups. While one may find that he or she likes or dislikes piezos, the real requirement is to get the best possible sound out of your piezo equipped instrument.
Piezo pickups are most often found in acoustic guitars, but also appear in acoustic basses, in mandolins with internal pickups and even more esoteric instruments. For example, my Emerald Guitars Symmetry 20 Harp guitar has piezo pickups for both the six string neck and the sub bass string set.
While we know that for live performance and studio recording we always have the option to set a microphone up to record an acoustic instrument, this does not help when we have a hybrid electric guitar that has both a magnetic pickup structure as well as a piezo system to give the guitar a pseudo acoustic output option.
In this article, we will explore methods for both live performance as well as some studio tips for recording any instrument that uses a piezo electric pickup system.
Regular readers may be shaking their heads at this topic, because they know that I really dislike the sound from piezo electric pickups. This is true, but I own instruments with piezo systems and replacing them may not be viable, or I may want to record the guitar without having to resort to a couple of microphones and all that miking guitars for recording entails.
What is Piezo Electric?
Piezo electricity was discovered in the 1880s. It is a measure of electric charge that accumulates in some materials when placed under some form of stress. While different materials can exhibit the effect, pickups tend to use crystals or ceramics or bone that accumulate electric charge under stress, in our case, the stress created by the vibrations of a string. The piezo electric material must be in direct or highly conductive contact with the string, so we tend to find that piezo electric pickups are typically found in, or directly under the bridge saddle or saddles, where the string rests. There are also contact type pickups that use the piezo electric effect to transform the electrical charge accumulated back into sound.
Piezo electric pickups are very high impedance devices, and the voltage delivered is measured as capacitance. Thus most piezo electric pickups go through some form of buffer amplifier to maximize frequency response. This is required because a piezo electric sensor does not respond equally to all frequencies. This buffer amplifier is designed in direct conjunction with the sensor element to output a more balanced tone that does not have significant peaks and troughs in the frequency response curve coming from an instrument. This is why we can find piezo electric pickups in other instruments such as orchestral strings and even harps.
Piezo Response
Since most musicians could not care less about the physics of piezo electricity, and have the good sense to shun the complex mathematics, the only value judgement made is the quality of the sound. Quality is highly subjective and requires some kind of frame of reference, that frame of reference most commonly being the natural unamplified frequency response of the instrument. This makes the piezo design challenging because different instruments respond differently based on materials, construction techniques and a variety of other factors. Thus, just like any other pickup, the body of the instrument has an effect on the sound reproduced by any pickup of any type. While individual pickups also have their own design and delivery structures, the instrument body is making a contribution to the total sound. While this statement may offend those who believe that construction methods and materials are irrelevant to the final sound of an instrument with a pickup of any kind, the physics and acoustic data says otherwise.
Thus musicians will listen to the unamplified instrument, and then listen to it from the pickup and commonly discern some differences. Using a full range flat response amplifier / speaker system is critical to make these value judgements and that is why acoustic instrument amplifiers are fundamentally different from electric instrument amplifiers and often also have a voice channel.
When queried about what they hear, or don’t hear, active listeners will often characterize piezo response as very bright, and while the plethora of adjectives used is a long list, bright, spiky, piercing, trebly, sizzley all apply. What active listeners will often identify as missing is the deep low end or what one may refer to as natural undertones, the subtle octave downs that a vibrating string will naturally generate and that the body of an open acoustic instrument naturally reinforces. Players who switch from a jumbo body to a parlour body will often say that the parlour has more high end and less bass compared to the jumbo. The frequency response of the strings may be identical, but the body is influencing the subjective tone. Piezo electric pickups are sometimes described in this way, that the bass is reduced or it sounds like there is a low cut filter in place, cutting off everything below a certain frequency.
Remedies for Piezo Effects
The primary remedy for the deleterious effect of piezo pickups is the use of equalization of the output signal from the instrument before it hits the preamplifier section of the amplifier, mixing board or recording interface. Some makers do this by adding a preamplifier into their overall piezo electric system, which includes some level of rudimentary tone controls, that on close examination are more treble cuts than equalization tools. The most common route is the use of an equalization pedal between the instrument and the input of the amp, mixer or interface, although the recording engineer may prefer to have the equalization applied during the recording or mixing steps. I speak of both options because many guitar players are now plugging into an interface and using a computer to do effects and mixing, or plugging into a digital modelling device to do effects there.
If you do not have a tame sound engineer at hand, the graphics equalizer pedal is the least expensive and simplest route. You don’t need a dozen bands, but three are not enough. A seven band eq is an excellent start, and I would propose the BOSS GE-7 as an excellent and inexpensive option. You can use it to bring back bass that is missing from the piezo system, and also to tamp down the sibilance and higher overtones and it’s very clear to see where things are when you have it set. This type of pedal also allows the player to optimize for room response, although you either need a good engineer providing guidance from the listener perspective, or you need someone to strum the guitar while you wander about the listening area to hear what you think is missing or overpowering. A decent EQ will also have a clean boost and this can be advantageous in providing both a volume boost as well as taking advantage of how the human ear responds to volume.
There are many fine EQ pedals available. My personal favourite is the EQ2 from Source Audio, but you should pick your own by going to a good music store and trying a few out. If that’s not possible, a BOSS GE-7 is low cost and will solve most all problems.
Another type of equalization is a body resonance pedal. TC Electronic builds one called the BodyRez and many musicians like it for its utter simplicity. It takes the form of a mini stomp pedal and has a single knob. It is used to restore the feel of the instrument body that may be diminished or lost by the use of the piezo electric pickup. I use one whenever I play an instrument that has a piezo pickup because it gets me into the ballpark very quickly and reduces the time that I need to spend on fine EQing. I even use it when I am plugging the guitar direct to desk and so run the guitar to the BodyRez and the output to input of the interface. When recording, I do not use an EQ pedal, instead I will use an EQ in the recording process, tending to favour plugin versions of classic Pultec equalizers, because I like the sound.
Your Piezo Supportive Pedal Board
While many acoustic instrument players run direct to an amp, or a PA for live, or to the interface for recording, I have discovered through experience that those whose skills and demands are more advanced typically have some form of effects board. Whether that is a pedal board, or in amp, or a set of plugins in the DAW is whatever works for you, but for simplicity a small portable pedal board is a great lower cost solution. There are many board makers in the market, I use PedalTrain although D’Addario has a nice system as well. The first pedal is always a tuner as I recommend pedal tuners over the headstock mounted types for serious work. Pick a tuner that you like, just be sure that you can read it when standing, and it is advantageous if the tuner acts like a mute while you are tuning. Then your Body Rez, then the equalizer pedal. Some players will add a compressor pedal and or a looper pedal to this simple one row board, and put a power supply affixed to the underside so you need only run one cable from the board to the AC power. My personal setups for acoustic include all these things. For acoustics, I like the Empress Compressor Mk II, and the TC Electronic Ditto+ looper. My go to power supply units are CIOKS DC7 units. Tech21NYC, like some others, including BOSS, make single units effects that contain all of the above (less the Body Rez) that may be more to your liking. I have had excellent results with the Tech21NYC Acoustic FlyRig in this scenario, although as I age, I find the knobs are getting smaller and harder to see.
Whatever you choose in this regard, it needs to be compact, easy to use and not requiring of menu diving and the need for an extra arm and a blood sacrifice to use and most importantly, it needs to put back what the piezo misses and take away what the piezo adds that you do not like.
Recording a Piezo Equipped Instrument
I’ve learned that younger players have no fear of recording themselves and are highly likely to dive into this wonderful pastime. I haven’t been young for some time in body, but I too get great enjoyment from the recording process. Most all Digital Audio Workstation software comes with a bunch of core effects plugins and while the Body Rez may not be one of them at this time, there are superb graphic and even better parametric equalizers either in the DAW or inexpensively purchased from companies such as WAVES. The same is true for compressors, and of course because you are recording, all DAW software supports multiple tracks and will often contain flexible backing track options to add drums and other instruments if you are on your own.
I admit upfront to being very picky about sound. For this reason, in the DAW I will always use some type of channel strip when recording. Again I will use channel strip plugins to add that studio feel and it is always the first plugin. There are excellent channel strips that sound like vintage NEVE, SSL or Avalon channel strips. These are typically not part of the DAW package, but you can purchase them separately if you are so inclined. I have found the Avalon 737 channel strip to be particularly nice with a piezo pickup, providing analog warmth along with its other benefits. I am grateful to the producer in Ireland from whom I learned this. Note that most Universal Audio channel strips require that you be using a Universal Audio interface. UADx and Waves channel strips do not require a specific interface.
Wrapping it Up
If your instrument came equipped with a piezo electric pickup, or that’s what was installed after the fact, there is no reason to fret about the sound quality. All piezos will need a bit of help. They are simple to use, and where there is a battery for a buffer amplifier, those batteries tend to last quite well so long as you unplug the instrument when not in use. Don’t spend a lot of time fretting about too brittle highs or perceived missing in action low end, these simple steps can bring sonorous pleasure to your piezo equipped instrument without the hassle and cost of directly miking the instrument. How do I know? Because I’ve taken the time to do the work in production.
Please note that when playing acoustic instruments live or for recording that do not use piezo electric pickups, I still use a tuner, an EQ, a compressor and a looper. Regardless of pickup system if you want an incredible acoustic amplifier that works great with piezos particularly, take a look at the Laney A-Duo. In my opinion, it kicks anything else in its price range and considerably higher to the curb. It’s very close to the audio quality of my AER acoustic amps.
Thanks as always for reading and your support of That Guitar Lover. I’m Ross Chevalier and until next time, peace.
